Dual Active Bridge based Micro-Inverter for Standalone Renewable Energy Systems with Low DC Link Capacitance

Abstract

Micro-inverters are required to interface PV generation directly with AC loads or grid at low power levels. A typical microinverter consists of a DC/DC conversion stage, followed by an inverter stage. Dual active bridge (DAB) converter appears to be a promising candidate for use in the DC/DC converter stage in a microinverter since it offers several features like high voltage gain, galvanic isolation, zero voltage switching, etc., which are highly desirable for microinverters applications. A micro-inverter topology is presented in this paper which is based on the dual active bridge converter. The proposed topology also incorporates active power decoupling (APD) by supplying the low frequency component of single phase AC power drawn by the load without using any extra switch. APD allows reduction in the required value of DC link capacitance without having a large voltage ripple. This obviates the use of electrolytic capacitors, which generally have a short operating life and are considered a weak link in power electronic systems. The paper describes the modelling of DAB for closed loop control, and the control system for 100 Hz power decoupling. The proposed microinverter topology has been simulated in PLECS, and the simulation results are presented here.